Our local BB had the 55LW5600 on display, and running the LG-provided 3D demo. This provided a decent exposure to the passive 3D, but there was no way to look at other content.
That said, based on what I saw, I would say that the reviews seen so far are pretty much on-target. Good/fair/decent/comparable to other quality-brand mid-range edge-lit LED-LCDs in 2D, and the 3D performance is basically as advertised.
The lines are visible in 3D mode if you get within 4 or 5 feet (55 inch set), but (for me at least) being 6 feet away solved this issue (and I will have a normal viewing distance at home in the 8-10 foot range). The side angle performance was very good, I thought, and more than adequate. I had heard concerns about ghosting of the 3D if the vertical angle was a bit much, but in the store the vertical angle had to be pretty high before I saw any significant ghosting. The resolution issue (due to each eye only seeing 540 lines) in 3D also wasn't significant to me, at least as long as I was 6 feet away. Someone above has commented about some off-color lines being visible at the bottom of the screen in 3D mode. I saw this, too - it seems like perhaps the bottom 2 lines. But this was also a non-issue at more than 6 feet.
The 3D demo content included an underwater/tropical fish section, a short "3D gaming" section, and a 3D sports demo. The fish section was very good, I thought, at a variety of viewing positions and angles. I suppose all 3D is like this, but moving around a bit made the big fish follow you around, and the "back" of the view also moved, while maintaining the depth of the 3D effect. And tilting of the head had minimal effect, although obviously the 3D content is made with basically horizontal eyes in mind... The 3D game demo (basically a dragon flying around) was pretty good also, although not any sort of gaming response time test. I would say that the B-ball 3D demo was the weakest, although this may have been due to the choice of content, more than the set. It seemed like the depth of focus wasn't that good, independent of the 3D. (I've seen 3D football demos on other sets which seemed better - it would have been nice to see the same demo on this set...)
I'm not a gamer, so the response-time issues that others have experienced isn't a big deal for me. It may be that a good plasma set's 3D will be of somewhat higher quality. But based on what I saw, the advantages of being able to have enough glasses on hand for a room-full of people, with pretty good 3D at different viewing points, more than makes up for any issues. And the 3D looked VERY competitive to the active 3D sets I've seen (Samsung LED-LCD, Sony LED-LCD, and Panasonic plasma).